Subj : HVYRAIN: Excessive Rainfa
To   : All
From : Mike Powell
Date : Tue Jan 27 2026 09:29:20

FOUS30 KWBC 270803
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
303 AM EST Tue Jan 27 2026

Day 1
Valid 12Z Tue Jan 27 2026 - 12Z Wed Jan 28 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Wegman


Day 2
Valid 12Z Wed Jan 28 2026 - 12Z Thu Jan 29 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

A cold front associated with a low that will track into the Gulf of
Alaska will move into the coast of the Pacific Northwest on
Wednesday. By the time that front moves into the coast, however, it
will be well detached from its parent low in the Gulf of Alaska,
which will be shearing apart in the mountains. The flow out of the
subtropics ahead of the front will provide some additional moisture
to be wrung out in the mountains of the Olympic Peninsula, however,
moisture flux will only ever be modest at best, with IVT values
topping out around 500 kg/ms. 

Model guidance suggests total rainfall into Western Washington has
decreased over the last 24 hours, with maximum rainfall amounts in
the Olympic Mountains around 3-4 inches, and lower amounts towards
the coast, around 1-2 inches. This modest rainfall (for this area)
when added to already dry soils and below average river flows,
should preclude any but very isolated flooding. In coordination
with SEW/Seattle, WA forecast office, the inherited Marginal Risk
was downgraded with this update.

Wegman


Day 3
Valid 12Z Thu Jan 29 2026 - 12Z Fri Jan 30 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

The inherited Marginal Risk across Western Washington was
downgraded to no risk areas with this update. A second wave
traveling northeast along the same front that will bring rainfall
to western Washington from Day 2 will track in similar fashion
roughly parallel to the coast and into British Columbia. This will
leave western Washington with a weaker, shearing apart area of
lighter rain. Rainfall forecast amounts have decreased with this 
update. Despite the rivers and streams becoming more elevated,
likely back to normal levels after Wednesday's rains, Thursday's
expected rainfall will be less, and remains unlikely to result in
flash flooding. With the downgrade of the Day 2 Marginal and in 
coordination with SEW/Seattle, WA forecast office, the Day 3 
Marginal was also downgraded with this update.

Wegman
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